Facebook’s privacy practices have always been controversial. It doesn’t charge its users–because its users are the product. The company sells information on its users, their social networks, services they like, and a multitude of other forms of information to advertisers and marketers. This gives Facebook a strong incentive to push privacy boundaries constantly, since the more personal information Facebook gathers on its users, the more money Facebook will be able to make by selling this information on to marketers.

This has meant, for example, that Facebook has frequently changed its privacy policies, often in confusing ways. Jennifer Shore and Jill Steinman, two undergraduate students at Harvard have just published a new research article in Technology Science showing that, over time, these changes have led to Facebook’s privacy policy becoming much, much worse.